From the Guardian articles it's becoming clearer that Mossack Fonseca is not some sort of mafioso outfit. Even the Guardian's own coverage has to admit that they do have compliance staff, do perform due diligence and do report things to the authorities. And they did close down operations when they got wind of illegal doings. So any stories have to become arguments about specific cases and debates about whether they could have done more in those cases, rather than the more juicy story they clearly want, implying that MF is some sort of criminal nexus that is being taken down by the journalistic establishment.
If we look at the Swiss banking leak from a few years ago, there were thousands of account details leaked to the UK government which assigned hundreds of tax officers to investigate them. And it turned out that about two thirds of them had paid exactly the right amount of tax all along. Of the rest, actually proving criminal intent turned out to be impossible, so of the original 1000+ account holders, only one case was ever actually taken to court. The others were cleared up through fines. The resulting amount of revenue was trivial at only £135 million, probably the costs of the investigation itself consumed most of that. This wasn't UK specific, other countries also ended up finding the data was useless for prosecutions.
The same was true of another case, when the Swiss authorities agreed to start sending tax information to the UK. The government thought it was in for a windfall and wrote the expected amounts into the budget. Red faces followed when the actual amount of unpaid tax turned out to be much lower than hoped for.
Maybe the Iceland angle will result in a few heads rolling, who knows, but I'm willing to bet that most of these revelations end up having very little impact: the worst cases are all in places where the local law enforcement is too weak to prosecute presidents and other heads of state for corruption.